1. Field of the Invention
This invention relates to an image processing system for generating an area-filled or painted image that is reproduced by an image reproducing device, such as an image display unit with a CRT or an image printer with a print head, and more particularly to an image processing system suitable for displaying an area filled image on a raster type CRT display.
2. Prior Art
Area-fill or painting is one of the basic image processing functions in an electronic image processing system, and various techniques have been heretofore proposed. The most basic technique is to use software for specifying areas to be filled in, and filling in the dots one by one for each pixel line in a random access memory so as to fill in all the pixels in the specified area. However, such area fill by software has the problem of requiring long processing time.
U.S. Pat. No. 4,189,743 to Schure et al discloses an area fill technique in which any one point in a closed contour line region written in a random access memory is selected as a seed point. The area fill is then performed first by filling a pixel line passing through the seed point in the range of the contour line, then, by filling in a pixel line adjacent to the first pixel line, and then repeating such procedure until area fill is completed. However, this technique requires a very complicated procedure.
Japanese Examined Patent Publication No. 40179/79 discloses a technique for displaying an area filled image in which a contour line pattern is written with some contour line dots selectively omitted so that each pixel line in a refresh memory includes an even number of contour line dots. As the pixel lines are read in synchronism with the CRT raster scanning, the video signal to the CRT is turned on at odd numbered contour line dots and turned off at even numbered contour line dots. However, the technique disclosed in this patent has problems in that: the distortion of the filled image, due to the omitted dots, is quite noticeable; processable images are limited; and an image cannot be processed in the refresh memory. In any event, the patent does not disclose the use of oriented vector data, and end point processing and area fill by exclusive OR as in the present invention.
The present invention seeks to provide an image processing system that can generate at high speed, and easily, a complicated, area filled image based on vector data representing a series of line segments constituting the contour of the image.